Are personality differences between twins predicted by astrology?

In Fuzeau-Braesch [Astrologie: La Preuve par Deux (1992a) and Personality and Individual Differences 13, 1135–1144 (1992b)] the parents of 238 pairs of twins matched brief astrological descriptions with their twinsʹ personalities and achieved 68.5% hits, very significantly better than the 50% expected by chance. The author concluded that astrology may be a “new element in differentiating personality within a pair of twins.” But we found reasons for doubt: her result is incompatible with previous findings, the disattenuated effect size is too high, the interval between births does not increase with increasing personality difference as required by her hypothesis, the astrological descriptions frequently differ from those prescribed by her supposedly objective rules, and the hit rate does not replicate. We then attempted to find an explanation for her results: we found evidence of artifacts in her reported data due to response set and stereotypes, and we found discrepancies between the reported data and the original data. Our re-analysis of the original data showed no significant deviation from chance. We conclude that an astrological explanation of Fuzeau-Braeschʹs results is unwarranted. The stereotype bias uncovered by us deserves to be added to the general list of human judgement biases.